“Early to bed and early to rise makes a man healthy, wealthy and wise.” –Benjamin Franklin
Some people are “morning people”, functioning a little too well in the early a.m. hours, while others are “lazy” and can’t get anything done before the crack of noon. When we fast forward the clock a bit to midnight or later, the morning people are out cold, whereas those lazy individuals are just getting revved up.
In a new study researchers Christina Schmidt and Philippe Peigneux, both at the University of Liège in Belgium, and their colleagues first asked 16 extreme early risers and 15 extreme night owls to spend a week following their natural sleep schedule. Then subjects spent two nights in a sleep lab, where they again followed their preferred sleep patterns and underwent cognitive testing twice daily while in a functional MRI scanner.
It is tempting to assign the blame for these differences on mere habit, but what if there is an underlying biological explanation? Perhaps there are other subtleties at play here as well.
An hour and a half after waking, early birds and night owls were equally alert and showed no difference in attention-related brain activity. But after being awake for 10 and a half hours, night owls had grown more alert, performing better on a reaction-time task requiring sustained attention and showing increased activity in brain areas linked to attention. More important, these regions included the suprachiasmatic area, which is home to the body’s circadian clock. This area sends signals to boost alertness as the pressure to sleep mounts. Unlike night owls, early risers didn’t get this late-day lift. Peigneux says faster activation of sleep pressure appears to prevent early birds from fully benefiting from the circadian signal, as evening types do.
An early riser who wakes up at 5 a.m. will not crash at 3 in the afternoon. However, their brains are not as alert in the late afternoon compared to a night owl who wakes up at noon, and is then tested past 10 p.m. The main difference is that night owls will maintain a high level of attention for longer periods of time, not just different periods of time.
Are night owls taking advantage of a circadian signal, or have they somehow pushed the brain’s equivalent of a snooze button, delaying the chemical reaction which causes the “need to sleep right now” pressure?
We would like to see a version of this study done with those individuals who naturally need 25% less sleep than normal.